1. Field of the Invention
This invention relates to cover stocks for golf balls having improved scuff resistance and golf balls having covers formed of the stocks.
2. Prior Art
In prior art golf balls, balata or trans-polyisoprene and ionomer resins are often used as the cover stock. Professional and skilled golfers prefer golf balls using balata as the cover stock, because the balata cover balls have good feel upon full shots with a driver and the ease of control (or spin susceptibility) upon approach shots.
The balata cover balls, however, have the drawback that the ball surface is marred or fluffed as a consequence of iron shots because the cover surface can be scraped by grooves across the iron club face. In addition, balata cover stocks are expensive and low in productivity because of difficulty to mold and a need for vulcanization.
Efforts have been made to seek for cover stocks having good feel and controllability comparable to the balata while eliminating the drawbacks of the balata. For example, cover stocks using thermoplastic polyurethane elastomers as disclosed in U.S. Pat. Nos. 3,395,109, 4,248,432, and 4,442,282 are relatively inexpensive as compared with the balata and easy to mold. Golf balls using these cover stocks offer good feel and controllability comparable to the balata cover balls. However, covers of thermoplastic polyurethane elastomers are still unsatisfactory in scuff resistance upon iron shots. Particularly at low temperatures or in winter, there is a likelihood that the ball surface can be cracked and dimples be scraped off by the iron club face.
Additionally, in golf ball cover stocks, metals salts of fatty acids such as magnesium stearate are generally blended as a dispersant. In a conventional process involving injection molding a cover stock having a fatty acid metal salt blended therein around a core to form a cover and painting the surface of the cover, the left-over of the fatty acid metal salt on the cover surface can adversely affect the adhesion of a paint coating to the cover.